This project is a continuation of research supported by EY 405 (and earlier USPHS grants) under the title "Information channeling in the retina". Because recent progress has resulted in some shifts in scope and emphasis, a different title has been used for this proposal -"Sensory mechanisms in visual orientation". Its primary objective is to study visual information processing with relevance to spatial orientation. Particular attention is focused on the mechanism of polarized light sensitivity and the channeling of the resulting information. Currently, three major aspects of this topic are being investigated. (1) Fine structural evidence of photoreceptor membrane recycling. Freeze fracture, electron opaque compartment markers and histochemical techniques are being employed. Crustacean rhabdoms are being used as the study system becuase the membrane turnover rate is several times faster than in the vertebrate system and because we have previously demonstrated the basic components of the lysosome-like sequence involved. (2) Behavioral studies of polarotaxis (e - vector orientation) in vertebrates to find response patterns useful in analyzing the mechanisms and significance of polarization sensitivity (PS) in this group. Both field and laboratory experiements have been carried out on this. (3) Continuing optical and electrophysiological studies designed to analyze the mechanisms of PS. At least two different systems are present. In rhabdoms, this depends on dichroism of the visual pigment in the microvilli of the photoreceptor membrane; in the fish we have studied, the mechanism seems to depend on differential light scattering within the retina itself.